The Atlantic Meridional Overturning Circulation (AMOC) is a vast, north-south system of currents that carries warm surface water towards the Arctic and returns colder water thousands of miles south through the deep ocean. It is a key component of the Earth's climate system, influencing the climate and weather of the UK and north-west Europe. However, the AMOC is under pressure due to global warming, and scientists are concerned about its potential to weaken or collapse.
The AMOC's influence on the UK's weather is significant. It helps shape the climate and weather patterns, and a weakening or collapse could lead to more extreme swings in the UK's weather, including colder winters, even as average global temperatures continue to rise. This is because the AMOC includes the Gulf Stream, which helps explain why Britain and north-west Europe are milder than their latitude would suggest.
The AMOC's weakening is already evident in a strange patch of cooling in the North Atlantic and changes in how salty the water is. Some researchers say the warning signs are visible, and the circulation may be less stable than previously thought. This raises the possibility that it could weaken sharply or even shift into a different state. In the most extreme scenario, some scientists warn it could 'collapse'.
However, others urge caution, saying weakening is not the same as collapse, and that the evidence may point to a slower decline or reorganisation rather than a sudden shutdown. But if the AMOC weakens significantly, it could shift storm tracks, alter rainfall and make winters more volatile. A severe weakening, or collapse, could bring colder, drier winters to the UK and north-west Europe even as the planet as a whole continues to heat up.
The AMOC's impact extends beyond the Atlantic. It helps shape rainfall and temperature patterns far beyond Europe, affecting harvests, water supplies and the livelihoods of hundreds of millions of people. The AMOC is part of a vast heat-moving system that influences the climate far beyond the Atlantic, and its weakening could have far-reaching consequences.
The AMOC's history provides a warning. In the past, the circulation has shifted abruptly, sending much warmer water towards eastern Canada. This suggests that the Atlantic circulation can be 'abruptly altered during climate change'. The AMOC's stability is a concern, and scientists are studying its potential to reach a tipping point.
The AMOC's tipping point risk is real, and it is not just that global warming could weaken the process. It is that, beyond a certain point, the weakening could begin to feed on itself. Warmer surface water is lighter, and extra rainfall and meltwater from ice make the ocean fresher. Fresher water is lighter too, and if the water in the high North Atlantic becomes too light, less of it sinks, leading to a feedback loop that could weaken the AMOC further.
The AMOC's weakening is evident in a 'cold blob' in the North Atlantic, which is a strange blue smudge in a sea of red on climate maps. This region is becoming less salty, and other studies point to changes in the Gulf Stream and signs that parts of the North Atlantic are being renewed more slowly. The AMOC's slowing is a concern, and it is already showing warning signs of the system reinforcing its own decline.
However, the evidence is complex, and the future of the system cannot yet be reduced to a simple story of imminent collapse. The AMOC's weakening would unfold in a warming world, and some of the cooling influence could be offset by the wider rise in global temperatures. The effect could be more complicated, with continued risk of extreme summer heat, greater exposure to cold winters, and more volatile weather generally.
The AMOC's weakening is a concern, and it is already showing warning signs of the system reinforcing its own decline. But the evidence is complex, and the future of the system cannot yet be reduced to a simple story of imminent collapse. The AMOC's weakening would unfold in a warming world, and some of the cooling influence could be offset by the wider rise in global temperatures. The effect could be more complicated, with continued risk of extreme summer heat, greater exposure to cold winters, and more volatile weather generally.
The AMOC's weakening is a concern, and it is already showing warning signs of the system reinforcing its own decline. But the evidence is complex, and the future of the system cannot yet be reduced to a simple story of imminent collapse. The AMOC's weakening would unfold in a warming world, and some of the cooling influence could be offset by the wider rise in global temperatures. The effect could be more complicated, with continued risk of extreme summer heat, greater exposure to cold winters, and more volatile weather generally.
The AMOC's weakening is a concern, and it is already showing warning signs of the system reinforcing its own decline. But the evidence is complex, and the future of the system cannot yet be reduced to a simple story of imminent collapse. The AMOC's weakening would unfold in a warming world, and some of the cooling influence could be offset by the wider rise in global temperatures. The effect could be more complicated, with continued risk of extreme summer heat, greater exposure to cold winters, and more volatile weather generally.
